As the concept of cloud computing is proposed and research and deployment of the cloud computing have made progress continuously, taking virtualization of a data centre as a development direction of the data centre has become a consensus in the industry. To put it simply, the data centre is a system containing infrastructures such as servers, storage devices, and a network connecting all the servers and storage devices. The virtualization of the data centre mainly refers to virtualization of the server and virtualization of a data network caused by the virtualization of the server. The so-called virtualization of a server is to allow to create multiple virtual servers which are called Virtual Station (VS in short) on one physical server, and each VS is configured with a separate Internet Protocol (IP in short) address and a separate Media Access Control (MAC in short) address and independently provides services outwards. In order to achieve mutual communication between VSs, the industry also introduces a concept of Edge Relay (ER in short) which can connect multiple VSs. The ER has two specific forms for implementation, with one called Virtual Edge Bridge (VEB in short), and the other one called Virtual Edge Port Aggregator (VEPA in short). The VEB is a virtual switch which has both a relay function and a switching function, and the VEB can directly achieve data communication between the connected VSs. The VEPA is a virtual device which only has a relay function but does not have a switching function, and the VEPA can not directly achieve the data communication between the connected VSs, but it can forward data received from the connected VSs to a physical switch for switching, and the VEPA also can forward data received from the physical switch to the connected VSs, thereby achieving the data communication between the connected VSs by using an external physical switch connected to a physical server.
Because of the rapid development and a large number of actual deployments of the data centre server virtualization technology, it is often required to create multiple ERs on one physical server at the same time. In order to distinguish and identify these ERs, it is required to create multiple channels logically isolated from each other (logical channel in short) between the physical server and the external physical switch, each logical channel corresponding to one ER and serving as a communication path of the VS connected by the ER. International Standard Organization Institute of Electrical and Electronics Engineers (IEEE in short) has developed a set of protocol mechanism to achieve automatic discovery and automatic establishment of a logical channel between a physical server and an external network edge physical switch, and this set of protocol mechanism is called S-Channel Discovery and Configuration Protocol (CDCP in short), which has been taken as a portion of the 802.1Qbg Edge Virtual Bridging (EVB in short) standard and approved by the IEEE in May, 2012.
The IEEE 802.1Qbg defines the whole EVB architecture. FIG. 1 is a schematic diagram of EVB architecture according to the related art. As shown in FIG. 1, one EVB station (i.e., a physical server supporting EVB) may contain multiple ERs, and each ER may connect multiple Virtual Station Interfaces (VSI in short) via multiple Downlink Relay Port (DRP in short), each VSI representing one virtual station. In order to distinguish different ERs, an S-virtual local area network (S-VLAN) component is introduced in the EVB architecture, and the S-VLAN component inside an EVB station and the S-VLAN component inside an EVB bridge (i.e., a physical switch supporting EVB) together form multiple logical S-channels isolated from each other, wherein each S-channel is connected to an Uplink Relay Port (URP in short) of a certain ER and a certain Station-facing Bridge Port (SBP in short) of a tenant identifier encapsulation component inside the EVB bridge. Each of the S-Channel Access Ports (CAP in short) of the S-VLAN component is connected to the URP and SBP correspondingly. An logical port on another side of the S-VLAN component is called Uplink Access Port (UAP in short), and the CDCP protocol defined by the 802.1Qbg standard as mentioned above is operated between the UAP inside the EVB station and the UAP inside the EVB bridge. The logical S-channel is implemented on a data plane by adding an S-VLAN Tag (S-TAG in short) which corresponds to the S-channel to a data frame entering the S-channel, and removing the S-TAG which corresponds to the S-channel from a data frame exiting from the S-channel. With reference to Table 1, Table 1 describes the specific encapsulation format of the S-TAG stipulated by the IEEE 802.1Q-2011 standard.
TABLE 1TPID (16 bits)PCP (3 bits)DEI (1 bit)SVID (12 bits)
As shown in Table 1, the S-TAG contains 16-bit Tag Protocol Identifier (TPID in short), 3-bit Priority Code Point (PCP in short), 1-bit Drop Eligible Indicator (DEI in short), and 12-bit S-virtual local area network identifier (SVID in short). The TPID carries a fixed Ethertype value stipulated by the standard, wherein the Ethertype value allocated by the 802.1Q-2011 standard to the S-TAG is 0x88A8. The PCP and DEI are used for identifying Quality of Service (QoS in short) of the Ethernet frame. The SVID is a field for distinguishing and identifying different logical S-channels in the S-TAG
The IEEE 802.1Qbg standard defines a protocol message encapsulation format of the CDCP, and illustrates a protocol communicating process of the CDCP in detail. The protocol message of the CDCP adopts the same outer layer encapsulation as a Link Layer Discovery Protocol (LLDP in short) message defined by the IEEE 802.1AB-2009 standard, and carries specific message contents by means of an encapsulation form of CDCP TLV (type, length, and value). The CDCP is a one-way protocol operated between the UAP of the EVB station and the UAP of the EVB bridge. There is a 1-bit Role field in the CDCP TLV for distinguishing that the sender of the current protocol message is the EVB station or EVB bridge. In addition, the S-VLAN component inside the EVB station and the S-VLAN component inside the EVB bridge respectively operate a CDCP protocol state machine, and complete the transition of a protocol state according to the received protocol message of the CDCP. With reference to FIG. 2, FIG. 2 is a flowchart of a protocol communicating process of the CDCP defined by the IEEE 802.1Qbg standard according to the related art. It should be noted that, in FIG. 2, each step in the protocol communicating process of the CDCP is not executed according to a time order, but triggered by a corresponding CDCP protocol state. The protocol communicating process of the CDCP in the related art includes the following major steps.
Step S201, after the CDCP protocol is initiated, a logical port UAP inside the EVB bridge sends a CDCP message to a logical port UAP inside the EVB station, in order to inform the EVB station of a maximum number of the S-channels supported by the logical port UAP inside the EVB bridge.
Step S202, after the CDCP protocol is initiated, the logical port UAP inside the EVB station sends a CDCP message to the logical port UAP inside the EVB bridge, in order to request SVIDs from the EVB bridge for each S-channel according to the number of S-channels required inside the EVB station.
The CDCP message for requesting SVIDs sent by the EVB station contains multiple pairs of (SCID, SVID) information, wherein the SCID represents an S-Channel ID, which is assigned by the EVB station. In the multiple pairs of (SCID, SVID) information, apart from a necessarily contained default S-channel (1, 1) stipulated by the protocol, SVIDs in the rest pairs are all fixedly set to be an unavailable value 0, representing that the SVIDs have not been allocated yet, and requesting the EVB bridge to perform allocation. For example, if three ERs are contained inside the EVB station and it is required to establish three logical S-channels for external communication of the three ERs, the CDCP message sent to the EVB bridge by the EVB station contains four pairs of (SCID, SVID) information in total, i.e., {(1, 1), (2, 0), (3, 0), and (4, 0)}, to request the EVB bridge to respectively allocate SVIDs to S-channels of which S-channel IDs are 2, 3, and 4.
Step S203, when the CDCP message for requesting SVIDs sent by the EVB station is received by the logical port UAP inside the EVB bridge, the logical port UAP inside the EVB bridge sends a CDCP message to the logical port UAP inside the EVB station, in order to allocate an SVID for each requested S-channel.
The CDCP message for allocating SVIDs sent by the EVB bridge contains multiple pairs of (SCID, SVID) information, wherein the SCIDs are consistent with the SCIDs carried in the CDCP message which is received by the EVB bridge and sent by the EVB station. In the multiple pairs of (SCID, SVID) information, apart from a necessarily contained default S-channel (1, 1) stipulated by the protocol, SVIDs in the rest pairs are all allocated with available values. For example, if the EVB station sends a request for establishing three logical S-channels and if the CDCP message sent by the EVB station to the EVB bridge contains four pairs of (SCID, SVID) information in total, i.e., {(1, 1), (2, 0), (3, 0), and (4, 0)}, the CDCP message sent by the EVB bridge also contains four pairs of (SCID, SVID) information in total, i.e., {(1, 1), (2, 7), (3, 345), and (4, 10)}, to respectively allocate SVID available values 7, 345, and 10 to the S-channels of which S-channel IDs are 2, 3, and 4.
Step S204, after the CDCP message for allocating SVIDs sent by the EVB bridge is received by the logical port UAP inside the EVB station, the logical port UAP inside the EVB station sends a CDCP message to the logical port UAP inside the EVB bridge, to inform the EVB bridge of the SVIDs that have been configured for each S-channel by the EVB station.
The CDCP message indicating the SVIDs that have been allocated sent by the EVB station contains multiple pairs of (SCID, SVID) information, wherein the SCIDs keep unchanged. In the multiple pairs of (SCID, SVID) information, apart from a necessarily contained default S-channel (1, 1) stipulated by the protocol, SVIDs in the rest pairs are all allocated with available values, representing that after the SVIDs allocated by the EVB bridge are received, they have been configured and taken effect at the EVB station. For example, if the EVB station sends a request for establishing three logical S-channels and if the CDCP message sent by the EVB bridge to the EVB station contains four pairs of (SCID, SVID) information in total, i.e., {(1, 1), (2, 7), (3, 345), and (4, 10)}, to respectively allocate SVID available values 7, 345, and 10 to the S-channels of which S-channel IDs are 2, 3, and 4, then the CDCP message sent by the EVB station to the EVB bridge also contains four pairs of SCID and SVID information in total, i.e., {(1, 1), (2, 7), (3, 345), and (4, 10)}, to confirm that the EVB station has respectively configured SVID available values 7, 345, and 10 for the S-channels of which S-channel IDs are 2, 3, and 4.
The IEEE 802.1AX-2008 standard defines a single node link aggregation technology, which is to logically bind multiple physical links at one node which are connected to the same adjacent node so as to be used as one logical link (i.e., a Link Aggregation Group, LAG in short), achieving the load sharing of service traffic among these multiple physical member links constituting the LAG, and under the condition where some of the member links have a fault, fast switching the service traffic to other member links which are with no fault, thus achieving the redundancy protection function. Currently, the IEEE 802.1AX-REV project is revising and expanding the single node link aggregation technology defined by the 802.1AX-2008 standard, and aims to formulate a cross-node link aggregation working mechanism that can logically bind multiple physical links at one or more nodes which are connected to multiple different adjacent nodes so as to be used as one logical link. The purpose of the cross-node link aggregation technology is consistent with that of the single node link aggregation technology, i.e., the purpose is to achieve the load sharing and redundancy protection of the service traffic among the LAG member links. The 802.1AX-REV draft standard (version D0.2, published in May, 2012) stipulates that, during the implementation of the cross-node link aggregation technology, one or more nodes at a side of the LAG constitute a portal together; and if multiple nodes constitute a portal, there should be a physical link between every two of the multiple nodes, wherein the physical link is called Intra-Portal Link (IPL in short) and is regarded as a channel of exchanging information required for completing the link aggregation by multiple nodes in one portal, and node ports used as two ends of the IPL are called Intra-Portal Link Port (IPP in short). In addition, the 802.1AX-REV draft standard further stipulates that, during the implementation of the cross-node link aggregation technology, the service traffic should perform the load sharing among the LAG member links on the basis of an outer layer VLAN tag, that is to say, data frames carrying different outer layer VLAN tags (i.e., different VIDs are contained in the outer layer VLAN tag) are allocated to different physical member links for transmission according to a certain algorithm. With regard to a specific allocation algorithm, the draft standard has not stipulated yet, but it is required that the two portals at two sides of the LAG adopt the same allocation algorithm so as to ensure that, at both directions of the LAG, the same physical member link is selected for data frames carrying the same outer layer VLAN tag.
In current actual deployments of the data centre, for achieving high bandwidth and high reliability of a server when accessing an external network, the server is required to access two network edge physical switches via two physical ports at the same time, and this access manner is called dual-homing access. Currently, the most common method for server dual-homing access is to use the cross-node link aggregation technology. Combining the current EVB architecture defined by the 802.1Qbg standard and the method that use the cross-node link aggregation technology to achieve server dual-homing access, FIG. 3 is a schematic diagram of architecture in which an EVB station accesses two EVB bridges in a dual-homing manner according to the related art. As shown in FIG. 3, the S-VLAN component inside the EVB station is respectively connected to the S-VLAN component inside EVB bridge 1 and the S-VLAN component inside EVB bridge 2; the EVB station itself constitutes one LAG portal at one side of the LAG; and the EVB bridge 1 and the EVB bridge 2 constitute one LAG portal at the other side of the LAG, and the EVB bridge 1 and the EVB bridge 2 are connected by the IPL.
However, the CDCP protocol defined by the currently formulated IEEE 802.1Qbg standard is only applicable to the condition where an EVB station operating the protocol accesses one network edge physical switch via one physical port, but can not be applied to the condition where an EVB station operating the protocol uses the cross-node link aggregation technology to access two network edge physical switches in a dual-homing manner via two physical ports.
With regard to the problem that the CDCP protocol can not be used to achieve that an EVB station accesses two network edge physical switches in a dual-homing manner via two physical ports in the related art, no effective solution has been presented.